A typical broadband microwave receiver or transmitter for an electronic warfare (EW) front-end is not only required to meet tight gain specifications over a wide operating temperature range typically −54° C. to +85° C. for an airborne environment but must also operate across wide bandwidths (an octave or more), such as 2-18 GHz or wider.
In order to meet gain specification, existing arrangements comprise the once-off manual tuning of the response so as to meet the required gain specification. Such a manual tuning may comprise the manipulation of tuning stubs while viewing the frequency response using microwave network analyser. This current approach is not only time consuming and costly requiring highly skilled technicians to interpret the response variation from each stage of tuning, but is unable to account for dynamic gain-affecting factors, such as temperature.
While dynamic compensation exist within the prior art, such dynamic compensation is limited to narrowband application, and at least on account of gain drop-off with frequency, are unable to provide adaptive gain shaping across wide bandwidth, as is required for LW front ends in dynamic gain affecting conditions.
For example, U22008/0119148 A1 (Ray) relates to system for Low-noise amplifier (LNA) adjustment to compensate for dynamic impedance matching. Specifically, in Ray, performance is optimised by adding matching components to minimise reflections. These matching components are located at the point of the mismatch between two components in the circuit (typically the antenna).
US2009/0130991 A1 (Rofougaran et al) relates to storing radio station settings in accordance with location.
Furthermore, reference is made to FIG. 1 showing a comparison 50 of prior art arrangements and the embodiments described herein. Specifically, FIG. 1 shows a gain comparison of the frequency response of prior art narrow band matching 101 (such as provided by Ray) and the gain shaping 102 according to the embodiments described herein. Specifically, the prior art 101 offers device matching by using inductors and capacitors (or other elements such as transmission lines) to change the impedance presented to a device.
However, as is evident from the prior art 101, the gain drops off at higher frequencies rendering such prior art tuning techniques ill-suited for generating a flat response across a Wide bandwidth. Now, in many applications, such prior art approaches may be preferred as most applications have narrow bandwidth operating requirements. However, as alluded to above, EW front-ends operate over wide bandwidths, such as across 3-20 GHz as is provided by FIG. 1.
Existing arrangements that attempt to provide matching of impedance across a wide bandwidth require that the matching components must be placed as close to point of mismatch as possible. As the physical distance between the mismatch and the matching components increases, the rate of change in electrical distance between the components also increases leading to a greater change in the impedance presented across frequency. Furthermore, the majority of components do not have a constant impedance versus frequency that could easily be matched out using a single component across a wide instantaneous bandwidth, and therefore the performance of existing matching options is limited.
In contradistinction, the present embodiments described herein allow for dynamic gain shaping across wide bandwidths (described herein as across at least an octave of bandwidth) as is evident from the gain response of the present embodiments 101 showing the flatness of the matched circuit having a 3 dB flatness bandwidth of about 8 GHz to 11.1 GHz.
It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.